What happens when food coloring molecules move, or DIFFUSE through gelatin, the substance that makes jello jiggle?
This creative science experiment that my kids and I invented lets you play with floatation physics by sprinkling glitter on melted gelatin, watch colorful dyes diffuse to create patterns and then use cookie cutters to punch out sticky window decorations. Water will evaporate from the gelatin, leaving you with paper-thin “stained glass” shapes.
You can watch us making them on Kare11 Sunrise News by clicking here.
-plain, unflavored gelatin from the grocery store or Target
–a drinking straw
*You can use the recipe below for two pans around 8×12 inches, or use large, rimmed cookie sheets for your gelatin. For a single pan, cut the recipe in half.
Step 1. Add 6 packs of plain, unflavored gelatin (1 oz or 28 gm) to 4 cups of boiling water. Stir well until all the gelatin has dissolved and remove bubbles with a spoon.
Step 2. Allow gelatin to cool to a kid-safe temperature. Pour the liquid gelatin into two large pans so it’s around 1-1.5 cm deep. It doesn’t have to be exact.
Step 5. In the pan with no glitter, use a straw to create holes in the gelatin, a few cm apart, scattered across the surface. It works best to poke a straw straight into the gelatin, but not all the way to the bottom. Spin the straw and remove it. Then, use a toothpick or skewer to pull out the gelatin plug you’ve created. This will leave a perfect hole for the food coloring. Very young children may need help.
Step 6. Add a drop of food coloring to each hole in the gelatin.
Step 7. Let the gelatin pans sit for 24 hours. Every so often, use a ruler to measure the circle of food coloring molecules as they diffuse (move) into the gelatin around them (read about diffusion at the bottom of this post.) How many cm per hour is the color diffusing? Do some colors diffuse faster than others? If you put one pan in the refrigerator and an identical one at room temperature, does the food coloring diffuse at the same rate?
Step 8. When the food coloring has made colorful circles in the gelatin, use cookie cutters to cut shapes from both pans of gelatin (glitter and food coloring), carefully remove them from the pan with a spatula or your fingers, and use them to decorate a window. (Ask a parent first, since some glitter may find its way to the floor!) Don’t get frustrated if they break, since you can stick them back together on the window.
Step 9. Observe your window jellies each day to see what happens when the water evaporates from the gelatin.
When they’re dry, peel them off the window. Are they thinner than when you started? Why? Can you re-hydrate them by soaking the dried shapes in water?
The Science Behind the Fun:
Imagine half a box filled with red balls and the other half filled with yellow ones. If you set the box on something that vibrates, the balls will move around randomly, until the red and yellow balls are evenly mixed up.
Scientists call this process, when molecules move from areas of high concentration, where there are lots of other similar molecules, to areas of low concentration, where there are fewer similar molecules DIFFUSION. When the molecules are evenly spread throughout the space, it is called EQUILIBRIUM.
Lots of things can affect how fast molecules diffuse, including temperature. When molecules are heated up, they vibrate faster and move around faster, which helps them reach equilibrium more quickly than they would if it were cold. Diffusion takes place in gases like air, liquids like water, and even solids (semiconductors for computers are made by diffusing elements into one another.)
Think about the way pollutants move from one place to another through air, water and even soil. Or consider how bacteria are able to take up the substances they need to thrive. Your body has to transfer oxygen, carbon dioxide and water by processes involving diffusion as well.
Why does glitter float on gelatin? An object’s density and it’s shape help determine its buoyancy, or whether it will float or sink. Density is an object’s mass (loosely defined as its weight) divided by its volume (how much space it takes up.) A famous scientist named Archimedes discovered that any floating object displaces its own weight of fluid. Boats have to be designed in shapes that will displace, or push, at least as much water as they weigh in order to float.
For example, a 100 pound block of metal won’t move much water out of the way, and sinks fast since it’s denser than water. However , a 100 pound block of metal reshaped into a boat pushes more water out of the way and will float if you design it well!
What is the shape of your glitter? Does it float or sink in the gelatin?
Here’s a video I made for KidScience app that demonstrates how to make window gellies
Credit: My 11 YO daughter came up with the brilliant idea to stick this experiment on windows. I was just going to dry out the gelatin shapes to make ornaments. Kids are often way more creative than adults!
When I was growing up, we always had a vegetable garden. My mom grew up on a farm and was appalled when my sister or I would throw a fit upon finding a tiny bug in our lovely, homegrown lettuce salad. “Where do you think the lettuce came from?” she would ask, and we’d have to admit that it grew in dirt, outside, and that there are bugs out there. It was an invaluable lesson and one I hope I can pass along to my kids. Our world has become too sterile and disconnected from nature. Like plants, we need dirt, sunshine, fresh air and clean water to survive. Who cares about a few bugs?
Try planting a few bean and pea sprouts in plastic bags to show your kids how sunshine and water can make a plant sprout!
You’ll need a few plastic zip-lock bags, dry beans from your pantry (or peas and beans from the garden seed packs you can find almost anywhere ), paper towels and water. Cut a paper towel so that you can fold it a few times and it will fit into the zip-lock baggie. Have your child soak it with water and help them put it into the bag so that it’s relatively flat. Then, give them two beans or seeds to place in the bag, near the bottom. I had to stuff a little piece of paper towel into the bottom of the bags so that the seeds wouldn’t sit in the extra water at the bottom. Let your child help seal the bag. Leave an opening near the top so the plants can get some air. Finally, tape the bag in a window with the beans facing you so that your child can watch them as they grow. (I’d recommend finding a window where they won’t get blasted by hot sun all day, or they might fry.)
As you do the project, ask your child what they think plants need to grow (Plants need light, air, water and nutrients, or “food.”) Ask them how they think the seed can grow without the dirt as “food.” Tell them that when a plant first sprouts, it gets its nutrients from the seed itself. They can watch the seed shrink as the plant grows. Have them draw the seed/plant in their science notebook as it changes. Older kids can measure the plants as they grow. Eventually, you should be able to transplant them to a cup with dirt, or directly into a garden. You may have to add water to the paper towels if they dry out. Play it by ear.
Plant a garden this spring, even a very tiny one in pots! Let your kids get their hands in the dirt. Help them nurture plants that will eventually nurture them. (Children are much more interested in tasting vegetables that they’ve grown themselves. ) It is one of the most rewarding activities you can do with your children, and takes only dirt, seeds and water! Find your inner farmer and let your children find theirs- organic food is cheap when you grow it yourself!